4J29 alloy is also known as the Kovar alloy, is a Nickel-Cobalt-Iron alloy having substantially the same thermal expansion characteristics as borosilicate glass (~5 × 10−6 /K between 30 and 200 °C, to ~10 × 10−6 /K at 800 °C) to allow a tight mechanical joint between the two materials over a range of temperatures.  It’s used in glass-to-metal seals in scientific apparatus, and conductors entering glass envelopes of electronic parts such as vacuum tubes (valves), X-ray and microwave tubes and some lightbulbs.

Kovar/4J29 Alloy Material Chemical Composition %

	C	Si	Mn	P	S	Ni	Fe	Cu	Cr	Co	Mo
Max	0.03	0.3	0.5	0.02	0.02	28.5–29.5	bal	0.2	0.2	16.8–17.8	0.2

Kovar/4J29 Mechanical property & Physical properties:

Yield Strength(Mpa)	Tensile Strength(Mpa)	Elongation(%)	Hardness(HRC)	Density
344	517	30%	78HB	8.36g/cm^3

We supply 4J29 Capillary Tubes in below materials and sizes:

Material: 4J29, UNS K94610, W.Nr.1.3912

Outside Diameter: 0.2 – 8 mm (0.00787 – 0.315 in.)

Wall Thickness: 0.015 -0.5 mm (0.00197 -0.0787 in.)

Length: Cut to Lengths according to required specifications